Tribological behaviour of an electrochemical jet machined textured Al-Si automotive cylinder liner material

- Electrochemical Jet Machining was used to texture a hyper-eutectic Al-Si alloy.
- Textured features exhibited no evidence of edge burs or lips.
- Friction coefficients were reduced by up to 38.5% as a result of the texturing.
- Texturing enhanced debris removal, preventing formation of a surface tribo-layer.

This paper investigates the use of Electrochemical Jet Machining to surface texture a hyper-eutectic Al-Si cylinder liner material. Samples were lapped to a 6 μm finish followed by immersion in 1 mol NaOH to expose the primary silicon colonies above the aluminium surface. Texturing was carried out using a NC system comprising of a fine gauge nozzle (cathode) jetting a solution of 2.3 mol NaCl on the surface (anode) whilst applying a current density of 220 A/cm2. An array of hemispherical dimples at 1.5 mm spacing was created, with an average diameter of 420 μm and depth of 40 μm, corresponding to an ε ratio of 0.095. Lubricated reciprocating sliding was carried out at stroke length of 25 mm in a bath of PAO (4 cSt) against a 52100 cylinder of 6mm diameter and 16mm length. Sliding frequencies were incremented at 1 Hz intervals between 1-15 Hz at 50 N load increments from 50-200 N. Stribeck curves indicated a reduction of the friction coefficient due to texturing of up to 0.05 in the mixed lubrication regime, representing a decrease of 38.5%. Optical profilometry and SEM indicated that abrasion and formation of a surface tribo-layer was mitigated in regions of the Al-Si surface where textured features were present parallel to the sliding direction.

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